The invention relates to an apparatus for releasing a predetermined amount of a free-flowing medium into a fluid container, in particular the flushing cistern of a WC.
As the free-flowing medium, in particular foaming agents, foam or the like are provided. The foaming agent serves to produce a closed-pore carpet of foam within a toilet bowl or similar vessel. Trials have shown that the most commonly used foaming agents and/or the foam they generate tend to acquire a "gelatinous" quality when they are in contact with air, with the result that after the apparatus has not been used for a long time, the discharge opening or valve for the foaming agent or foam becomes occluded. Hence after a long period of disuse the apparatus is no longer functional.
The German patent DE 39 08 178 A1 discloses an apparatus of the kind cited above. In this apparatus the container for the free-flowing medium is constructed as a flexible bag, into which the medium is put without any air inclusions. As the flowing medium is released, the bag collapses correspondingly, so that no introduction of air can occur. The flowing medium is coupled to an input of a diaphragm pump by way of a nonreturn valve. At an output of the diaphragm pump an outlet pipe is attached by way of another nonreturn valve. The open end of the outlet pipe is situated in a fluid container. The diaphragm pump comprises a flat diaphragm, which is deformed by means of an actuating plunger. The actuating plunger is moved by a float attached to a lever. The lever is one-sided, such that the float is further away from the fulcrum of the lever than is the actuating plunger. Hence the force acting on the plunger is greater than the force generated by the buoyancy of the float. In an alternative embodiment, the float is disposed below the plunger. In this case the buoyancy of the float is equal to the force with which the plunger acts on the diaphragm. If the fluid container is a flushing cistern for a WC, one pumping cycle of the diaphragm pump corresponds to a single process of flushing and refilling the cistern.
Such an apparatus has the disadvantage that for the flat diaphragm a relatively large amount of force must be applied. Furthermore, the use of a lever makes the construction relatively elaborate. A diaphragm pump with a flat diaphragm also has the disadvantage that the change in volume is relatively small in comparison to the volume of the pumping chamber. The result is that the size of the discharged dose of flowing medium is limited; in addition, the dosage cannot be precisely determined. The shape of the pumping chamber furthermore makes it more likely that residues of the flowing medium will remain therein. The known apparatus, finally, has the further disadvantage that it is relatively cumbersome to install in a flushing cistern. The apparatus must be attached to the cistern at several points. Moreover, the apparatus or at least its supporting device must be matched to the particular cistern with respect to its geometric dimensions. Hence for nearly every type of cistern it is necessary to have a special embodiment of the apparatus described above, or of its supporting device. Therefore the manufacturing costs are high.
Taking as a starting point the state of the art according to DE 39 08 178 A1, it is the object of the present invention to make available an apparatus for releasing a predetermined amount of a free-flowing medium in which the force to operate the diaphragm pump is reduced, the relative volume change in the pumping chamber is increased and the construction is made less elaborate. Furthermore, the apparatus is designed to be installable by simple means in nearly all commercially available flushing cisterns, the number of fixation elements being kept as small as possible.